It has been known for several decades that microwave energy can be used to excite certain molecular species and particularly water molecules and hydroxyl radicals. Furthermore, the microwave excitation can penetrate several centimeters into materials containing water or hydroxyl radicals. The heating effects generated by this molecular excitation are the basis for microwave cooking of food and the drying of damp or water-containing materials.
This invention proceeds from the unexpected effect of microwave energy upon particulate ores or concentrates which have been previously intimately admixed with either an already active form of carbon or with some other carbon-containing material which can readily be dried and heated to charring temperatures by microwave energy.
Not only has microwave energy been found to rapidly dry and heat these admixtures but also reduction reactions can be initiated within the mixtures.